A method of making a pack for food and the associated pack

ABSTRACT

A method of making a pack for food comprising the following steps. Forming a tray by providing a tray laminate comprising a fibrous web ( 21 ) bonded to a web of a gas barrier film ( 20 ) comprising a multi-layer laminate comprising a heat sealable layer and a gas barrier layer. Vacuum and/or thermoforming the laminate to create a tray with an upstanding rim. Filling the tray with a food product (F). Providing a web of lid film ( 13 ), the lid film ( 13 ) being a gas barrier film comprising a multi-layer laminate comprising a heat sealable layer and a gas barrier layer. Heat sealing the lid film ( 13 ) to the gas barrier film of the tray around the periphery of the tray to create a hermetic seal between the two barrier films. Severing the pack from the webs of material.

The present invention relates to a method of making a pack for food. Inparticular, the invention is directed at an improvement of a pack forfood of the type which comprises a shallow tray hermetically sealed by afilm lid. Such packs are widely used for the packaging of flat foodssuch as sliced meat and cheese. They can, however, be used for any typeof food which can be fitted into a relatively shallow container.

Traditionally, the tray is made from a thermoformed plastic and a filmlid is heat sealed to the tray to create a hermetically sealed closurefor the food. A separate sticker is then adhered to the completed packto provide information concerning the contents of the pack andpromotional information.

For environmental reasons, there is a need to reduce the amount ofplastic used in packaging.

A recent development of a pack of this type is a tray which is formed ofa fibrous material such as paper which is provided with an extrusioncoating of a polymer. However, such a coating is not suitable for useswhere a modified atmosphere (i.e. where a pack is filled with a gasother than air) is required where gas transmission needs to beprevented. The present invention aims to provide a pack which reducesthe amount of plastic involved, but which can also provide a good gasbarrier such that it is suitable for modified atmosphere applications.

According to the present invention there is provided a method accordingto claim 1

By providing a tray which is a laminate of the fibrous web and a gasbarrier film, the tray is able to reduce significantly the amount ofplastic required as compared to a conventional plastic tray. Further, asthe tray has a laminated gas barrier film, the film is much more readilyable to form a reliable gas barrier seal than the extrusion coating ofthe prior art. This is because a multi-layer film can be used, withenhanced barrier properties to provide a hermetic seal with the barrierfilm of the lid. The extrusion coating process used in the prior art islimited to a simple, single layer material such that it is not suitablefor providing complex film properties.

The lid may comprise just the barrier film layer. However, preferably,the lid film is part of a lid laminate further comprising a secondfibrous web adhered to the lid film to create a lid laminate before thestep of heat sealing the lid film to the tray.

This provides a fibrous layer on both the base and the lid of thecontainer which has a pleasant “natural” feel for a consumer. It alsoallows printing to be applied directly to the fibrous web on the trayand/or the lid thereby removing the need to apply a sticker to the packin order to provide the necessary information on the pack contents. Thisprovides a much simpler manufacturing process and also creates a muchnicer looking pack.

The method preferably also further comprises cutting a window in thesecond fibrous web before adhering it to the lid film. By cutting thewindow before adhering the second fibrous web to the lid film, awell-defined window can be created without the possibility of cuttinginto the film and spoiling the integrity of the pack. Again, this stepprovides a pack with good aesthetic appeal in which the user can see thecontents of the pack.

The fibrous web of the tray is preferably able to provide most of thestructural integrity of the tray with the amount of plastic in the gasbarrier film being minimised whilst ensuring that it is sufficient toprevent any moisture passing into the fibrous web and also to providethe hermetic seal with the lid film. Preferably, therefore, the fibrousweb in the tray is at least three times, preferably at least four timesand most preferably at least five times thicker than the gas barrierfilm of the tray.

The present invention also extends to a pack according to claim 7.

The pack has the advantages described above in relation to the firstaspect of the invention. It also preferably has the second fibrous webcreating the lid laminate and the window in the lid as well as theoptional printing described above.

The reference to a gas barrier film in this context is a film which willprovide a significant barrier to the flow of gas through the matrix offilm itself (as opposed to any faults, tears or pinholes created atedges of the film). In particular, we are concerned with a film whichwill prevent the flow of oxygen. Food packages are frequently providedwith a modified atmosphere, for example by being flushed with a gas(e.g. nitrogen) or by being evacuated thereby reducing as much aspossible the level of oxygen within the food pack. The purpose of a gasbarrier film is to provide a sufficient barrier to the gases normallyfound in air (particularly oxygen), that the atmosphere within thecontainer will remain within an acceptable oxygen level for the desiredshelf life of the product.

According to one definition, the gas barrier film should be sufficientto ensure that, in a hermetically sealed container, the film is able toprevent an oxygen level within the pack from rising from 1% (followingthe introduction of the modified atmosphere) to above 10% and preferablyabove 5% in 15 days (assuming normal storage and display at atemperature of less than or equal to 20° C.).

Put another way, the film should have barrier properties for oxygenwhich ensure that the film has an oxygen transmission rate of less than15 g/m²/24 hours. More preferably this is below 6 g/m²/24 hours (asdetermined by standard test ASTM D3985).

An example of a method and pack in accordance with the present inventionwill now be described with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic drawing showing the manufacturing process and FIG.2 is a cross-section through an edge of the pack showing the layerstructure.

With reference to FIG. 1, the materials required to create the liddingfor the final pack are supplied from two reels, 1, 2 in a lidmanufacturing stage L. The reel 1 supplies a web of fibrous lid material5. This may be, for example, a paper of 70 gsm. Having a thickness of 80microns. The fibrous lid material 5 may have been pre-printed on itsupper surface 6. Alternatively, the fibrous lid material 5 may beprinted in-line as part of the lidding production process by a printer7. The film then passes a cutter 8 which will cut apertures into the webwhich will become windows in the finished pack P.

The reel 2 supplies the gas barrier film for the lid. The film is amulti-layer high barrier film, where one side is a polyolefin, such as12-40 microns of Poly-Ethylene, which will form a heat seal layer. Theother surface of the film may be the same, or a different polymer, suchas 12-40 microns of PET. In addition, the film will contain typically1-5 microns of a barrier substance, such as EVOH or SiOx. Additionallayers and tie layers may also be present to complete the gas barrierfilm. The gas barrier lid film 9 may have antimist properties on theinternal, heatseal surface or a food grade antimist coating may beapplied separately before it passes below an adhesive applicator 11which applies a film of adhesive to the other side of film 9 before thetwo webs or material are brought together in a lamination region 12 tocreate a lid laminate 13. Alternatively, adhesive may be applied to thefibrous lid material 5.

The materials required to make the tray of the final pack are suppliedfrom two reels, 3, 4 in a tray manufacturing stage T. A gas barrier film20 is fed from the reel 3 past an adhesive station 21 which applies afilm of adhesive to the gas barrier film 20. This film is preferably aPE/EVOH/PE High Barrier film with or without additional layers and atotal thickness of typically 35-50 micron but could be any otherformable HB film. A web of fibrous tray material 21 is fed from the reel4. The fibrous tray material is a material of typically 200-400 micronthickness at (150-300 gsm) and may either be pre-printed or printed inline with this process, as described for the lidding material. Theadhesive may alternatively be applied to this material. The twomaterials 20, 21 are laminated at rollers 22 to produce a tray laminate23.

The final, sealed, packaging product, is produced on lines at a packmanufacturing stage P. Typically, this is done on a site where the packsare to be assembled and filled which is generally different to the sitewhere the lid laminate 13 and tray laminate 23 are formed. The traylaminate 23 is fed to a thermoforming tool 24 with a male die 25 andfemale die 26 in the shape of the tray. These apply heat and pressure tothe tray laminate 23 in a manner well known in the art to create arecessed tray shape having a depth of typically 15 mm. Alternativelythere may only be one die and a combination of air pressure and vacuummay be used to shape the web to the die, with or without the applicationof heat. Although the schematic drawing shows only one such tray beingformed, in practice, there will be an array of male and female dies suchthat multiple tray shapes will be formed in the web across and along thebase laminate 23 simultaneously.

The tray laminate 23 then passes to a filling station 28 and a conveyor29 where the recessed tray shapes are filled with a stack of food itemsF or an individual item. The tray laminate 23 then passes on theconveyor 29 beneath a roller 30 which receives the lid laminate 13. Thelid laminate 13 is pressed onto the tray laminate and heat is appliedaround the rim of each tray using a heat sealing platen to create acontinuous heat seal between the two laminates to hermetically seal thelid to the container.

The combined laminates which have now been filled are then fed by theconveyor 29 to a cutter 32 where the individual packs P are cut from theweb.

The detail of the pack is shown in FIG. 2. This shows the four layerstructure comprising the fibrous lid material 5 and the lid film 9 whichare joined together by an adhesive 40 as described above to create thelid laminate 13. The fibrous lid material 5 terminates at an edge 41providing exposed film 42 which provides the window formed by cuttersinto an inner cavity 43 in which the food is positioned.

The tray film 20 is adhered to the fibrous tray material 21 by anadhesive 44 as described above to create the tray laminate 23. Therecessed shape which is apparent from FIG. 2 is the shape which isformed in the thermoforming process by the thermoforming tool 24.

At the lip of the tray, there is a region 45 where the films 9, 20 areheat sealed to one another around the full periphery of the tray therebyensuring that the enclosure 43 is hermetically sealed. This region 45may extend in certain regions almost to the outer periphery of the rim.However, in at least one region, ideally a corner portion, there ispreferably a release region 46 where the films are left unconnectedallowing the user to peel apart the film 9, 20 starting from thisregion.

The finished product is one which can be made on a continuous basis on aweb-based system. Two webs are brought together in a manner which cancreate a hermetically sealed container with gas barrier properties whichrequires significantly less plastic than in the prior art. The fibrouslayers can be printed with full colour printing directly onto the packremoving the need for a sticker. Also, different and distinctive shapesof windows can readily be created simply by changing the cutter 8. Thefinished pack can therefore be made to have a striking overallappearance as well as having a pleasant and more natural feel of afibrous container as opposed to the conventional plastic.

1. A method of making a pack for food, the method comprising the stepsof: forming a tray by providing a tray laminate comprising a firstfibrous web bonded to a web of a gas barrier film comprising amulti-layer laminate comprising a heat sealable layer and a gas barrierlayer; vacuum and/or thermoforming the laminate to create a tray with anupstanding rim; filling the tray with a food product; providing a web oflid film, the lid film being a gas barrier film comprising a multi-layerlaminate comprising a heat sealable layer and a gas barrier layer;adhering a second fibrous web having a window to the lid film to form alid laminate; heat sealing the lid film to the gas barrier film of thetray around the periphery of the tray to create a hermetic seal betweenthe two barrier films; and severing the pack from the webs of material.2. (canceled)
 3. (canceled)
 4. A method according to claim 1, whereinthe first fibrous web of the tray is at least three times the thickness,preferably at least four times the thickness and more preferably atleast five times the thickness of the gas barrier film of the tray.
 5. Amethod according to claim 1, further comprising the step of printing onthe first fibrous web of the tray prior to creating the tray laminate.6. A method according to claim 1, further comprising the step ofprinting on the second fibrous web prior to creating the lid laminate.7. A pack for food, the pack comprising a tray thermoformed from alaminate of a fibrous web and a web of a gas barrier film into a traywith an upstanding rim, and a gas barrier film lid heat sealed to thesheet of gas barrier film in the tray around the periphery of the trayto create a hermetically sealed enclosure between the two barrier films.8. A pack according to claim 7, wherein the lid is a laminate of asecond fibrous web and the gas barrier film.
 9. A pack according toclaim 8, further comprising a window in the second fibrous web.
 10. Apack according to claim 7, wherein the fibrous web is printed.
 11. Apack according to claim 8, wherein the second fibrous web is printed.12. A pack according to claim 7, wherein the heat sealable layer is apolyolefin.
 13. A pack according to claim 7, wherein the gas barrierfilm is ethylene vinyl alcohol copolymer (EVOH) or silicon oxide (SiOx).14. A pack according to claim 7, wherein the heat sealable layer has ananti-mist coating.
 15. A method according to claim 1, wherein the heatsealable layer is a polyolefin.
 16. A method according to claim 1,wherein the gas barrier film is ethylene vinyl alcohol copolymer (EVOH)or silicon oxide (SiOx).
 17. A method according to claim 1, wherein theheat sealable layer has an anti-mist coating.